Military leaders called North Korea's cyber threat "real," Tuesday, and said there was a high possibility it will conduct an attack on South Korean communication networks during the G-20 Summit to be held in Seoul in November.

In a speech at a cyber security conference in Seoul, Minister of National Defense Kim Tae-young said North Korea is focusing on cyber terror attacks against South Korea, including the distribution of false information to Internet sites to defame the South Korean government.

"Though an investigation showed the Navy ship Cheonan was sunk by a North Korean military provocation and more than 50 countries support the results of the probe, North Korea continues to distort the truth and try to discredit our government and military in the online community," Kim said.

A Seoul-led multinational investigation group concluded last month that a North Korean midget submarine had torpedoed the 1,200-ton Cheonan after sneaking through international waters into the West Sea.

But rumors and suspicions have been lingering about the cause of the incident among the online community here and abroad. Some argue that the ship was sunk because of an accident or a problem with a naval exercise between the South Korean and U.S. navies.

During the conference, Maj. Gen. Bae Deuk-sik, commander of the DSC, said North Korea has been nurturing military hackers after selecting talented students at elementary school. "This is part of efforts to beef up the regime's cyber warfare capability, a key asymmetrical threat."

"To disturb the G-20 Summit, the North is likely to conduct a massive cyber attack, of which it is easy to destroy evidence," the commander said. "An individual organization can't defend against such an attack so all related government agencies should cooperate in establishing a seamless cyber defense posture."

Earlier this year, the defense ministry launched a cyber warfare command led by a major general.

Last year, the government and industrial computer networks suffered from massive distributed denial of service attacks for several days.

Intelligence sources blamed North Korea, though no solid evidence was found to support the claim.

The North is known to operate a cyber warfare unit that specializes in hacking into South Korean and U.S. military networks to extract classified information.